Scoring
Interpretation for a single table (or a single table SQL expression)

10

Perfect.
A full index can be used and the asterisk is not present.

8 - 9

Very
good. A full index can be used but the asterisk is present.
It can be improved a little by removing the asterisk.

7

Fine.
Here there are two interpretations:
1) A full index can be used and the asterisk is present. Better
modify to remove asterisk since it's moving a lot of data
for each record it selects.
2) A partial index can be used and the asterisk is not present.
You should evaluate how useful is the index that can be used.

4 - 6

Bad.
Access can always be improved. Asterisk is always present
and a full index cannot be used. A partial index can be used
but you should evaluate how useful is it.

0 - 3

Very
bad. No index can be used. Access must be improved or it may
represent a problem.

The
scoring of an SQL which handles more than one table is the average
of each table scoring. As a general rule an SQL scoring 7 or more
(green) is considered OK. You will always be able to improve SQLs
scoring less than 7.